Reference is hereby made to the following, commonly assigned, co-pending, U.S. Patent Applications which disclose common subject matter: Ser. No. 09/067,729 filed Apr. 28, 1998 for MULTIPLE CHANNEL, SEQUENTIAL, CARDIAC PACING SYSTEMS filed in the names of C. Struble et al.; Ser. No. 09/439,244 filed on event date herewith for MULTI-SITE CARDIAC PACING SYSTEM HAVING CONDITIONAL REFRACTORY PERIOD filed in the names of K. Kleckner et al.; Ser. No. 09/439,569 filed on even date herewith for CARDIAC PACING SYSTEM DELIVERING MULTI-SITE PACING IN A PREDETERMINED SEQUENCE TRIGGERED BY A SENSE EVENT in the names of C. Yerich et al.; Ser. No. 09/439,565 filed on even date herewith for BI-CHAMBER CARDIAC PACING SYSTEM EMPLOYING UNIPOLAR LEFT HEART CHAMBER LEAD IN COMBINATION WITH BIPOLAR RIGHT HEART CHAMBER LEAD in the names of B. Blow et al.; and Ser. No. 09/439,568 filed on even date herewith for RECHARGE CIRCUITRY FOR MULTI-SITE STIMULATION OF BODY TISSUE filed in the names of B. Blow et al.; and Ser. No. 09/439,243 filed on even date herewith for AV SYNCHRONOUS CARDIAC PACING SYSTEM DELIVERING MULTI-SITE VENTRICULAR PACING TRIGGERED BY A VENTRICULAR SENSE EVENT DURING THE AV DELAY in the names of C. Yerich et al.
The present invention pertains to multi-site cardiac pacing systems for pacing multiple spaced apart sites of a patient""s heart, particularly right and left heart chambers, e.g., the right and left ventricles, in triggered pacing modes while avoiding inappropriate, potentially pro-arrhythmic, triggered pacing in response to non-refractory sense events occurring early in the pacing escape interval
In diseased hearts having conduction defects and in congestive heart failure (CHF), cardiac depolarizations that naturally occur in one upper or lower heart chamber are not conducted in a timely fashion either within the heart chamber or to the other upper or lower heart chamber. In patients suffering from CHF, the hearts may become dilated, and the conduction and depolarization sequences of the heart chambers may exhibit Intra-Atrial Conduction Defects (IACD), Left Bundle Branch Block (LBBB), Right Bundle Branch Block (RBBB), and Intra Ventricular Conduction Defects (IVCD). In such cases, the right and left heart chambers do not contract in optimum synchrony with each other, and cardiac output suffers due to the conduction defects. In addition, spontaneous depolarizations of the left atrium or left ventricle occur at ectopic foci in these left heart chambers, and the natural activation sequence is grossly disturbed. In such cases, cardiac output deteriorates because the contractions of the right and left heart chambers are not synchronized sufficiently to eject blood therefrom. Furthermore, significant conduction disturbances between the right and left atria can result in left atrial flutter or fibrillation.
It has been proposed that various conduction disturbances involving both bradycardia and tachycardia of a heart chamber could benefit from pacing pulses applied at multiple electrode sites positioned in or about a single heart chamber or in the right and left heart chambers in synchrony with a depolarization which has been sensed at at least one of the electrode sites. It is believed that cardiac output can be significantly improved when left and right chamber synchrony is restored, particularly in patients suffering from dilated cardiomyopathy and CHF.
A number of proposals have been advanced for providing pacing therapies to alleviate these conditions and restore synchronous depolarization and contraction of a single heart chamber or right and left, upper and lower, heart chambers as described in detail in commonly assigned U.S. Pat. Nos. 5,403,356, 5,797,970 and 5,902,324 and in U.S. Pat. Nos. 5,720,768 and 5,792,203 all incorporated herein by reference. The proposals appearing in U.S. Pat. Nos. 3,937,226, 4,088,140, 4,548,203, 4,458,677, 4,332,259 are summarized in U.S. Pat. Nos. 4,928,688 and 5,674,259, all incorporated herein by reference. The advantages of providing sensing at pace/sense electrodes located in both the right and left heart chambers is addressed in the ""688 and ""259 patents, as well as in U.S. Pat. Nos. 4,354,497, 5,174,289, 5,267,560, 5,514,161, and 5,584,867, also all incorporated herein by reference.
The medical literature also discloses a number of approaches of providing bi-atrial and/or bi-ventricular pacing as set forth in: Daubert et al., xe2x80x9cPermanent Dual Atrium Pacing in Major Intra-atrial Conduction Blocks: A Four Years Experiencexe2x80x9d, PACE (Vol. 16, Part II, NASPE Abstract 141, p.885, April 1993); Daubert et al., xe2x80x9cPermanent Left Ventricular Pacing With Transvenous Leads Inserted Into The Coronary Veinsxe2x80x9d, PACE (Vol. 21, Part II, pp. 239-245, January 1998); Cazeau et al., xe2x80x9cFour Chamber Pacing in Dilated Cardiomyopathyxe2x80x9d, PACE (Vol.17, Part II, pp. 1974-1979, November 1994); and Daubert et al., xe2x80x9cRenewal of Permanent Left Atrial Pacing via the Coronary Sinusxe2x80x9d, PACE (Vol.15, Part II, NASPE Abstract 255, p. 572, April 1992), all incorporated herein by reference.
Significant conduction disturbances between the right and left atria can result in left atrial flutter or fibrillation that can be suppressed by pacing the left atrium synchronously with right atrial pacing or sensing of P-waves. And, cardiac output can be significantly improved when left and right chamber synchrony is restored, particularly in patients suffering from dilated cardiomyopathy and CHF.
However, in certain circumstances, the delivery of triggered pacing upon a non-refractory sense event is not desirable and might provoke a tachyarrhythmia. The above-incorporated, commonly assigned ""356 patent provides triggered pacing at two spaced apart sites in the right atrium in response to atrial sense events to suppress atrial tachyarrhythmias. A minimum time interval (APB interval) is timed out during the A-A escape interval, and triggered pacing at one or both of the atrial sites is provided only if an atrial sense event occurs after time-out of the APB interval and before the time-out of the A-A escape interval.
We have realized that this same precaution must be taken when triggered pacing pulses are delivered at spaced apart ventricular and right and left heart chamber sites.
The present invention is particularly directed to providing multi-site, ventricular and right and left heart chamber pacing systems and methods of operation that avoid triggering arrhythmia episodes.
The present invention may be applied to control a pacemaker having first and second pace/sense electrodes at first and second spaced apart sites of a single ventricular heart chamber or right and left heart chambers at the same level, i.e., the right and left atria or ventricles. It involves starting and timing out an escape interval and a trigger pace window that is shorter than the escape interval on a sense event or delivery of a pacing pulse through one of the pace/sense electrodes to one of the sites. And, if a sense event is detected during the timing out of the escape interval following the time-out of the trigger pace window, a pacing pulse or pacing pulses are delivered in a triggered pacing mode to a selected one or both of the first and second spaced apart sites of the heart through a respective one of both of said first and second pace/sense electrodes. But, triggered pacing is inhibited if the sense event is detected during time-out of the trigger pacing interval to avoid triggering arrhythmia episodes.
In the context of right and left heart chamber pacing systems, a number of triggered pacing modes are possible. In one triggered pacing mode, a first pacing pulse can be delivered to the right or left heart chamber and a second pacing pulse delivered to the left or right heart chamber, respectively, after a triggered pacing delay. The two pacing pulses can be delivered either upon a non-refractory sense event detected in one of the right or left heart chambers or upon time-out of a pacing escape interval. Alternatively, following a non-refractory sense event in the right or left heart chambers, a single pacing pulse can be delivered to the left or right heart chamber, respectively after time-out of the triggered pacing delay timed from the sense event. In still another triggered pacing mode, a single pacing pulse can be delivered to the left or right heart chamber where the non-refractory sense event is detected. However non-refractory sense events that occur too early in a cardiac cycle from a previous sense event or pace event are not employed to deliver triggered pacing to either or both of the right and left heart chamber.
In any of these triggered pacing modes, the delivery of a pacing pulse at the time-out of a preceding pacing escape interval or a non-refractory right or left chamber sense event during the pacing escape interval restarts the pacing escape interval, typical post-pace or post-sense refractory time periods, an upper rate interval, and the trigger pace window of the present invention. The trigger pace window extends beyond the refractory period and upper rate interval for a predetermined portion of the escape interval and times out before the pacing escape interval times out. A non-refractory sense event that occurs during the trigger pace window resets the pacing escape interval, but triggered pacing in response to it is disabled.
The present invention is preferably implemented in multi-site ventricular pacing systems, and in right and left heart chamber pacing systems providing bi-atrial or bi-ventricular pacing, and in three or four chamber pacing systems for providing bi-atrial and/or bi-ventricular pacing with AV synchronous pacing between the atria and ventricles.
The present invention is preferably implemented into an external or implantable pulse generator and lead system selectively employing right and left heart, atrial and/or ventricular leads. The preferred embodiment is implemented in an architecture that allows wide programming flexibility for operating in AV synchronous modes with right and left ventricular pacing or in atrial or ventricular only modes for providing only right and left atrial or ventricular pacing. The AV synchronous embodiments may be implemented into an IPG or external pulse generator and lead system providing right and left ventricular pacing and sensing and either both right and left atrial pacing or just right or left atrial pacing and sensing. Alternatively, the invention can be implemented in IPGs or external pulse generators and lead systems having hard wired connections and operating modes that are not as programmable.